Vertical Circulation Off the Ross Ice Shelf 
C. W. Thomas 1 
ABSTRACT: The Ross Ice Shelf is a floating ice mass about 200 m thick over 
an average depth along the barrier of 567 m. In January the prevailing wind blows 
from the east, parallel to the coast. The wind current transports the low salinity 
layer (ca. 50 m) toward the ice shelf, where it must descend. Directly off the bar- 
rier we find low salinities to a depth of 150 m. The circulation here is quite 
similar to that defined by Sverdrup along the shelf ice of Queen Maud Land. 
Because of sinking of the low salinity layer near the barrier, diatoms live in abun- 
dance at subcompensation depths, Trigonium arcticum actually on the sea bed. 
The southern boundary of the Ross Sea is 
fringed by floating ice of the Ross Ice Shelf ex- 
cept for the relatively small McMurdo Sound- 
Ross Island area. The clifflike barrier of the ice 
shelf is about 200 m thick (Sullivan, 1957). 
An average of 35 m rises from the surface of 
the water and about 165 m are submerged. The 
average depth along the barrier is 567 m. The 
width of the shelf in places exceeds 1300 km. 
Since water can circulate beneath this huge 
ice mass we can expect unique features of 
circulation. 
The Ross barrier is washed by the Circum- 
polar Countercurrent which is produced partly 
by the distribution of density and partly by the 
prevailing wind. This current is usually weak 
along the barrier, but as it sweeps around Cape 
Adare it often attains a velocity of about 3 
knots (author’s observation). The data shown 
in Table 2 for station G-l indicate that at this 
station a weak current is flowing toward the 
east. This supports the postulation of Kort 
(1962), who projected such a current through 
the vicinity of this station. 
In all, three stations were taken off Kainan 
Bay (Ross Ice Shelf) along a north-south line 
at distances of 0, 40, and 156 km (Fig. 1). 
Two of these were taken in edisto and one in 
GLACIER. The work was carried out under the 
general supervision of Dr. Willis L. Tressler of 
the U. S. Navy Oceanographic Office. Several 
1 Contribution No. 135, Hawaii Institute of Geo- 
physics, University of Hawaii, Honolulu. Manuscript 
received January 12, 1965. 
vertical plankton tows were made with a 20- 
mesh closing net at stations Ed-1 and Ed-2. 
The water column was sampled at all three of 
these stations. The results of these casts are 
shown in Tables l 2 and 2 respectively. 
2 Because of the wide variation in the size of biota 
the terms many, common, and few are used to con- 
note relative quantitative abundance. 
170* 180° 170° 
Fig. 1. Map showing locations of collecting stations. 
239 
